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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Exospheric temperature inferred from the Aeros-A neutral composition measurement

The derivation of exospheric temperature from satellite drag measurements is based on an assumption of invariant conditions of the neutral atmosphere at 120 km. Since it has been established that atomic oxygen, which is usually the major neutral constituent in the region of drag measurements, is subject to considerable variability with season, latitude, and solar and geomagnetic activity in the altitude region of 120 km, its value as an indicator of exospheric temperature is questionable. Ogo 6 neutral mass spectrometer measurements revealed that molecular nitrogen is a better indicator of exospheric temperature, since it is not subject to changes caused by eddy mixing and is therefore relatively less variable near the turbopause. However, theoretical arguments show that argon, even though it is a minor constituent, is relatively less variable with respect to changes in eddy diffusion coefficient and hence a better indicator of exospheric temperature than O and N2. In this paper the relative merits of these gases for deriving exospheric temperature are investigated by using observational data from the Aeros-A Nate experiment.

Chandra, S.↗
NASA NTRS2007

Polymer-Ceramic Composite Materials for Pyroelectric Infrared Detectors: An Overview

Ferroelectrics:Polymer composites can be considered an established substitute for conventional electroceramics and ferroelectric polymers. The composites have a unique blend of polymeric properties such as mechanical flexibility, high strength, formability, and low cost, with the high electro-active properties of ceramic materials. They have attracted considerable interest because of their potential use in pyroelectric infrared detecting devices and piezoelectric transducers. These flexible sensors and transducers may eventually be useful for their health monitoring applications for NASA crew launch vehicles and crew exploration vehicles being developed. In the light of many technologically important applications in this field, it is worthwhile to present an overview of the pyroelectric infrared detector theory, models to predict dielectric behavior and pyroelectric coefficient, and the concept of connectivity and fabrication techniques of biphasic composites. An elaborate review of Pyroelectric-Polymer composite materials investigated to date for their potential use in pyroelectric infrared detectors is presented.

Aggarwal, M. D↗
NASA NTRS2012

Flexible Thermal Protection System Development for Hypersonic Inflatable Aerodynamic Decelerators

The Hypersonic Inflatable Aerodynamic Decelerators (HIAD) project has invested in development of multiple thermal protection system (TPS) candidates to be used in inflatable, high downmass, technology flight projects. Flexible TPS is one element of the HIAD project which is tasked with the research and development of the technology ranging from direct ground tests, modelling and simulation, characterization of TPS systems, manufacturing and handling, and standards and policy definition. The intent of flexible TPS is to enable large deployable aeroshell technologies, which increase the drag performance while significantly reducing the ballistic coefficient of high-mass entry vehicles. A HIAD requires a flexible TPS capable of surviving aerothermal loads, and durable enough to survive the rigors of construction, handling, high density packing, long duration exposure to extrinsic, in-situ environments, and deployment. This paper provides a comprehensive overview of key work being performed within the Flexible TPS element of the HIAD project. Included in this paper is an overview of, and results from, each Flexible TPS research and development activity, which includes ground testing, physics-based thermal modelling, age testing, margins policy, catalysis, materials characterization, and recent developments with new TPS materials.

DelCorso, Joseph A.↗
NASA NTRS2012

Assimilation of GIRO Data into a Real-Time IRI

Increasingly accurate and detailed global 3-D specification of the Earth's space plasma environment is required to further understand its intricate organization and behavior. For a long time space physics and aeronomy research has been data starved due to the great variety of natural time scales involved in the plasma phenomenology. We have started developing a new approach to the global ionospheric specification called Real-Time Assimilative Mapping (RTAM). The IRI-RTAM will use data from the Global Ionospheric Radio Observatory (GIRO) to smoothly transform International Reference Ionosphere's (IRI's) background empirical maps of the ionospheric characteristics to match the observations. Such empirical assimilative modeling will provide a high-resolution, global picture of the ionospheric response to various short-term events observed during periods of storm activity or the impact of gravity waves coupling the ionosphere to the lower atmosphere, including timelines of the vertical restructuring of the plasma distribution. It will also contribute to the challenging task of providing a rapid insight into the temporal and spatial space weather development using the real-time GIRO data streams. The new assimilation technique "updates" the IRI electron density distribution while preserving the overall integrity of IRI s typical ionospheric feature representations. The technique adjusts the coefficients of the spherical/diurnal expansions used by the CCIR and URSI-88 model to obtain the global sub-peak electron density distribution. The set of global corrected coefficients can be generated as frequently as every 15 min and easily disseminated using a single real-time RTAM server operated by GIRO.

Galkin, I. A.↗
NASA NTRSDate not supplied

Wind Tunnel Testing of AFC over a Deflected Aileron on the High-Lift Common Research Model

Active flow control (AFC) using discrete fluidic actuators distributed along the span, just upstream of the deflected aileron of the 10% scale high-lift version of the Common Research Model (CRM-HL), was evaluated during a wind tunnel test in the NASA Langley 14- by 22-Foot Subsonic Tunnel. For this set of experiments, a new outboard section was fabricated incorporating a deflectable aileron. Aileron deflection angles of 0, 7.5, 16, and 25 were investigated. This experimental investigation is in response to a recent study by Boeing potential to use AFC with a drooped aileron during takeoff to improve lift-to-drag ratio (L/D) by as much as 5%, depending on AFC mass flow rate. AFC is used at deflection angles above the nominal deflection of 7.5 to control the resulting flow separation that occurs and potentially improve L/D. Improvements in aircraft low-speed L/D can affect vehicle range and/or payload. Tuft flow visualization data, steady and unsteady surface pressure data, and force and moment data are used to compare the flowfields with and without AFC. Parameters varied include actuator momentum coefficient and aileron deflection angle. The surface pressure and tuft flow visualization results indicate that without AFC, the flow over a majority of the aileron upper surface is separated for aileron deflection angles larger than 7.5. When AFC is applied, the flow is reattached to the aileron. Force and moment results show that a local increase in lift leads to an increase in L/D of at least 3.5% using mass flow rates thought to be available from air sources onboard a commercial transport.

AFC↗
NASA NTRS1992

Active and passive microwave measurements of soil moisture in FIFE

During the intensive field campaigns of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) in May-October of 1987, several nearly simultaneous measurements were made with low-altitude flights of the L-band radiometer and C- and X-band scatterometers over two transects in the Konza Prairie Natural Research Area, some 8 km south of Manhattan, Kansas. These measurements showed that although the scatterometers were sensitive to soil moisture variations in most regions under the flight path, the L-band radiometer lost most of its sensitivity in regions unburned for many years. The correlation coefficient derived from the regression between the radar backscattering coefficient and the soil moisture was found to improve with the increase in antenna incidence angle. This is attributed to a steeper falloff of the backscattering coefficient as a function of local incidence at angles near nadir than at angles greater than 30 deg.

Wang, J. R.↗
DOE OSTI2016

Switchable and tunable film bulk acoustic resonator fabricated using barium strontium titanate active layer and Ta{sub 2}O{sub 5}/SiO{sub 2} acoustic reflector

A solidly mounted acoustic resonator was fabricated using a Ba{sub 0.60}Sr{sub 0.40}TiO{sub 3} (BST) film deposited by metal organic chemical vapor deposition. The device was acoustically isolated from the substrate using a Bragg reflector consisting of three pairs of Ta{sub 2}O{sub 5}/SiO{sub 2} layers deposited by chemical solution deposition. Transmission electron microscopy verified that the Bragg reflector was not affected by the high temperatures and oxidizing conditions necessary to process high quality BST films. Electrical characterization of the resonator demonstrated a quality factor (Q) of 320 and an electromechanical coupling coefficient (K{sub t}{sup 2}) of 7.0% at 11 V.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Ladtap XL Version 2017: A Spreadsheet For Estimating Dose Resulting From Aqueous Releases

LADTAP XL© is an EXCEL© spreadsheet used to estimate dose to offsite individuals and populations resulting from routine and accidental releases of radioactive materials to the Savannah River. LADTAP XL© contains two worksheets: LADTAP and IRRIDOSE. The LADTAP worksheet estimates dose for environmental pathways including external exposure resulting from recreational activities on the Savannah River and internal exposure resulting from ingestion of water, fish, and invertebrates originating from the Savannah River. IRRIDOSE estimates offsite dose to individuals and populations from irrigation of foodstuffs with contaminated water from the Savannah River. In 2004, a complete description of the LADTAP XL© code and an associated user’s manual was documented in LADTAP XL©: A Spreadsheet for Estimating Dose Resulting from Aqueous Release (WSRC-TR-2004-00059) and revised input parameters, dose coefficients, and radionuclide decay constants were incorporated into LADTAP XL© Version 2013 (SRNL-STI-2011-00238). LADTAP XL© Version 2017 is a slight modification to Version 2013 with minor changes made for more user-friendly parameter inputs and organization, updates in the time conversion factors used within the dose calculations, and fixed an issue with the expected time build-up parameter referenced within the population shoreline dose calculations. This manual has been produced to update the code description, verification of the models, and provide an updated user’s manual. LADTAP XL© Version 2017 has been verified by Minter (2017) and is ready for use at the Savannah River Site (SRS).

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1995

The Dripping Handrail Model: Transient Chaos in Accretion Systems

We define and study a simple dynamical model for accretion systems, the "dripping handrail" (DHR). The time evolution of this spatially extended system is a mixture of periodic and apparently random (but actually deterministic) behavior. The nature of this mixture depends on the values of its physical parameters - the accretion rate, diffusion coefficient, and density threshold. The aperiodic component is a special kind of deterministic chaos called transient chaos. The model can simultaneously exhibit both the quasiperiodic oscillations (QPO) and very low frequency noise (VLFN) that characterize the power spectra of fluctuations of several classes of accretion systems in astronomy. For this reason, our model may be relevant to many such astrophysical systems, including binary stars with accretion onto a compact object - white dwarf, neutron star, or black hole - as well as active galactic nuclei. We describe the systematics of the DHR's temporal behavior, by exploring its physical parameter space using several diagnostics: power spectra, wavelet "scalegrams," and Lyapunov exponents. In addition, we note that for large accretion rates the DHR has periodic modes; the effective pulse shapes for these modes - evaluated by folding the time series at the known period - bear a resemblance to the similarly- determined shapes for some x-ray pulsars. The pulsing observed in some of these systems may be such periodic-mode accretion, and not due to pure rotation as in the standard pulsar model.

Young, Karl↗
NASA NTRS2018

Predictive Thermal Control (PTC) Technology to Enable Thermally Stable Telescopes

The Predictive Thermal Control (PTC) technology development project is a multiyear effort initiated in Fiscal Year (FY) 2017, to mature the Technology Readiness Level (TRL) of critical technologies required to enable ultra-thermally-stable telescopes for exoplanet science. During 2017/18 PTC has successfully progressed its three defined objectives: 1. Validate thermal optical performance models. 2. Derive thermal system stability specifications. 3. Demonstrate Predictive Thermal Control. by accomplishing or advancing three of its five quantifiable milestones: Milestone #1 (Complete): Created a high-fidelity STOP (Structural-Thermal-Optical-Performance) model of the1.5 meter ULE® AMTD (Advanced Mirror Technology Development)-2 mirror, including 3D CTE (Coefficient of Thermal Expansion) distribution and reflective coating, that predicts its optical performance response to steady-state and dynamic thermal gradients. Structural model was created using 3D X-Ray Computed Tomography; Milestone #2 (Complete): Derived specifications for thermal control system as a function of wavefront stability for a Vector Vortex Coronagraph; Milestone #3 (In-Process): Designed and started fabricating a predictive Thermal Control System for the AMTD-2 1.5 meter ULE® mirror that senses temperature changes and actively controls the mirror's thermal environment; Milestone #4 (In-Process): Performed preliminary STOP model validation tests of the 1.5-m ULE® mirror in a relevant thermal vacuum environment at the MSFC X-ray and Cryogenic Facility (XRCF) test facility; Milestone #5: Use validated model to perform trade studies to determine how thermo-optical performance can be optimized as a function of mirror design, material selection, mass, etc.

Stahl, H. Philip↗
NASA NTRSDate not supplied

Wind Tunnel Testing of AFC over a Deflected Aileron on the High-Lift Common Research Model

Active flow control (AFC) using discrete fluidic actuators distributed along the span, just upstream of the deflected aileron of the 10% scale high-lift version of the Common Research Model (CRM-HL), was evaluated during a wind tunnel test in the NASA Langley 14- by 22-Foot Subsonic Tunnel. For this set of experiments, a new outboard section was fabricated incorporating a deflectable aileron. Aileron deflection angles of 0, 7.5, 16, and 25 were investigated. This experimental investigation is in response to a recent study by Boeing potential to use AFC with a drooped aileron during takeoff to improve lift-to-drag ratio (L/D) by as much as 5%, depending on AFC mass flow rate. AFC is used at deflection angles above the nominal deflection of 7.5 to control the resulting flow separation that occurs and potentially improve L/D. Improvements in aircraft low-speed L/D can affect vehicle range and/or payload. Tuft flow visualization data, steady and unsteady surface pressure data, and force and moment data are used to compare the flowfields with and without AFC. Parameters varied include actuator momentum coefficient and aileron deflection angle. The surface pressure and tuft flow visualization results indicate that without AFC, the flow over a majority of the aileron upper surface is separated for aileron deflection angles larger than 7.5. When AFC is applied, the flow is reattached to the aileron. Force and moment results show that a local increase in lift leads to an increase in L/D of at least 3.5% using mass flow rates thought to be available from air sources onboard a commercial transport.

AFC↗
DOE OSTI2026

A buoyancy–shear–drag–scalar-based turbulence model for power-law acceleration-driven Rayleigh–Taylor, reshocked Richtmyer–Meshkov, and Kelvin–Helmholtz mixing

A previously developed phenomenological turbulence model for Rayleigh–Taylor, reshocked Richtmyer–Meshkov, and Kelvin–Helmholtz instability-induced mixing based on a general buoyancy–shear–drag model [O. Schilling, “A buoyancy–shear–drag-based turbulence model for Rayleigh–Taylor, reshocked Richtmyer–Meshkov, and Kelvin–Helmholtz mixing,” Physica D 402, 132238 (2020)] is extended to include active or passive scalar mixing and power-law acceleration-driven Rayleigh–Taylor mixing. The buoyancy–shear–drag equations are coupled to a scalar variance equation that is used to define the molecular mixing parameter θ m , and when the scalar is active, modifies the Rayleigh–Taylor and Kelvin–Helmholtz mixing layer growth parameters to depend on the asymptotic value of this parameter, θ mol . Here, the scalar variance equation is closed by algebraically or differentially modeling the scalar variance dissipation rate. Nonlinear analytical solutions of the model are obtained in the total and separate bubble and spike mixing layer width formulations with the algebraic scalar variance dissipation rate for each instability, which are then used to calibrate the mechanical and scalar equation coefficients to predict specific values of physical observables and molecular mixing parameters. Surrogate mechanical and scalar turbulent fields can be constructed by multiplying a presumed self-similar spatial profile by appropriate functions of the width and its time derivative, and of the scalar obtained by solving the ordinary differential model equations. The explicit modeling and solution of turbulent transport equations are not required. The bubble and spike mixing layer width and scalar variance equations are then solved numerically for constant-acceleration Rayleigh–Taylor, impulsively reshocked Richtmyer–Meshkov, and Kelvin–Helmholtz mixing, confirming that the prescribed level of molecular mixing is correctly predicted and illustrating the spatiotemporal evolution of the scalar fields.

Buoyancy–drag↗
DOE OSTI2024

Day-to-day reliability of basal heart rate and short-term and ultra short-term heart rate variability assessment by the Equivital eq02+ LifeMonitor in US Army soldiers

Introduction The present study determined the (1) day-to-day reliability of basal heart rate (HR) and HR variability (HRV) measured by the Equivital eq02+ LifeMonitor and (2) agreement of ultra short-term HRV compared with short-term HRV. Methods Twenty-three active-duty US Army Soldiers (5 females, 18 males) completed two experimental visits separated by >48 hours with restrictions consistent with basal monitoring (eg, exercise, dietary), with measurements after supine rest at minutes 20–21 (ultra short-term) and minutes 20–25 (short-term). HRV was assessed as the SD of R–R intervals (SDNN) and the square root of the mean squared differences between consecutive R–R intervals (RMSSD). Results The day-to-day reliability (intraclass correlation coefficient (ICC)) using linear-mixed model approach was good for HR (0.849, 95% CI: 0.689 to 0.933) and RMSSD (ICC: 0.823, 95% CI: 0.623 to 0.920). SDNN had moderate day-to-day reliability with greater variation (ICC: 0.689, 95% CI: 0.428 to 0.858). The reliability of RMSSD was slightly improved when considering the effect of respiration (ICC: 0.821, 95% CI: 0.672 to 0.944). There was no bias for HR measured for 1 min versus 5 min (p=0.511). For 1 min measurements versus 5 min, there was a very modest mean bias of −4 ms for SDNN and −1 ms for RMSSD (p≤0.023). Conclusion When preceded by a 20 min stabilisation period using restrictions consistent with basal monitoring and measuring respiration, military personnel can rely on the eq02+ for basal HR and RMSSD monitoring but should be more cautious using SDNN. These data also support using ultra short-term measurements when following these procedures.

General & Internal Medicine↗
NASA NTRS1972

Invariant poles feedback control of flexible, highly variable spacecraft.

This paper describes a technique for single-axis control of a model of a highly flexible Space Station. Active damping of lower frequency flexibility modes is employed. In the control technique, referred to as invariant poles feedback control (IPFC), feedback gains are adjusted so that the closed-loop system's characteristic equation is matched to that of a reference model; hence, closed-loop system's poles will not move - they will be invariant (provided bending frequencies and parameters can be identified accurately). This is accomplished by obtaining the system's characteristic equation in closed form; equating respective coefficients between terms of like powers in s in the system and reference model characteristic equations; and, solving for the feedback gains. The feedback gains are explicit functions of system plant parameters and the coefficients of the reference model's characteristic equation, and are easily programmed for the digital computer.

Mendel, J. M.↗
NASA NTRS1991

A video-aided study of sea spikes in radar backscatter at moderate incidence

Backscatter from a lake was measured at a 37-deg incidence angle using an FM-CW radar operating on X band and C band simultaneously. A limited amount of Ka-band data was also collected at 50 deg incidence. A video camera recorded the activity within the footprint looking upwind and crosswind. The video showed that breaking waves at all look directions and wedge-shaped waves when looking upwind consistently produced spikes in the radar time series. However, 62 percent to 90 percent of the spikes were not attributable to any surface structure visible on the video picture except wave crests. These spikes may be due to specular reflections or micro-scale breaking too small to be seen. Individual contributions to the backscattering coefficient were calculated for unattributed spikes, breaker spikes, and wedge spikes.

Bush, Daniel A.↗
NASA NTRS2019

ZERODUR Substrates for Application of High-Temperature Protected-Aluminum Far Ultraviolet Coatings

Recent development in coating deposition processes for aluminum mirrors that are protected with a metal-fluoride overcoat (such as LiF, MgF2, or LiF) have improved reflectance performance particularly in the far-ultraviolet (FUV) part of the optical spectrum. The active research in this area is motivated by the fact that these gains in reflectance are expected to significantly increase the throughput of any future FUV-sensitive NASA missions into the Lyman Ultraviolet. These reflectance improvements are attributed, in part, by performing the metal-fluoride overcoat depositions with the substrates at an elevated temperature as high as 220-250 degrees Celsius. ZERODUR® is a widely used material as a mirror substrate because, among other things, it exhibits a low coefficient of thermal expansion (CTE) over a wide range of temperatures. Moreover, ZERODUR® has recently been proposed for several future NASA concept missions where this improved FUV mirror coating may be used. Given the elevated temperature at which these improved FUV coatings are produced, it is imperative to make sure that heating of the substrate will not significantly impact the final figure of the coated mirror. In this paper, we will study and report the effects of heating ZERODUR® up to the highest temperature mentioned above (250 degrees Celsius) during a simulated coating process. These studies are relevant since it has been reported the CTE will change slightly if ZERODUR® is cooled down from application temperatures between 130 degrees Celsius and 320 degrees Celsius with rates that differ from the initial production annealing rate of 3 degrees Celsius per hour.

Engineering↗
NASA NTRS1999

Active Control of Flow Separation Over an Airfoil

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

Ravindran, S. S.↗
NASA NTRS1988

Laboratory studies of sticking coefficients and heterogeneous reactions important in the stratosphere

The discovery of ozone depletion during spring in the Antarctic stratosphere has received wide spread attention. Both meteorological and chemical mechanisms have been used in attempts to explain this observation. The chemical theory focused on the chlorofluoromethanes released into the atmosphere. However, gas-phase, homogeneous reactions alone in the model can not adequately explain such a depletion. Heterogeneous reactions on ice surfaces could be important in the Antarctic stratosphere. These reactions are thought to convert ClONO2 and N2O5 into HNO3 in the solid phase while Cl2, HOCl, and ClNO2 are released into the stratosphere as gas-phase products. The photolysis of Cl2, HOCl, and ClNO2, then produces active chlorine which subsequently removes ozone through several catalytic cycles, including the Cl2O2 mechanism. The polar stratospheric clouds are thought to consist of mixtures of water ice, nitric acid, and sulfuric acid. Condensation of HCl onto the PSC's could provide active surfaces for heterogeneous reactions.

Leu, Ming-Taun↗